Micro LED structure

ABSTRACT

The present invention discloses a micro LED structure including a first semiconductor layer, a first electrode, a second electrode, and an active layer. The first semiconductor layer has two opposite sides defined as a first surface and a second surface. The first semiconductor layer has a doped region located therein and exposed on the first surface. A pn junction is formed between the doped region and the first semiconductor layer. The first electrode and the second electrode, located on the first surface, are capable of electrically connecting to the first semiconductor layer and the doped region respectively. The active layer is adjacent to the second surface. Wherein the first semiconductor layer is a first doping type, and the doped region is a second doping type different from the first doping type, and the first semiconductor layer and the pn junction are located at identical side of the active layer.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention pertains to a micro light emitting diode, inparticular to a semiconductor structure of a micro light emitting diode.

2. Description of the Prior Art

Please refer to FIG. 1A. FIG. 1A is a schematic diagram illustrating asemiconductor structure of a conventional light emitting diode (LED). Asshown in FIG. 1A, a n-type semiconductor layer 90, an active layer 91and a p-type semiconductor layer 92 are stacked and formed on asubstrate 93 in manufacturing a conventional LED. Since it is necessaryto apply a driving current to the active layer 91, electrodes areusually disposed on the surfaces of the n-type semiconductor layer 90and the p-type semiconductor layer 92, such the electrodes can beelectrically connected to the power source by wire bonding. Taking FIG.1A as an example, since the p-type semiconductor layer 92 is sandwichedbetween the active layer 91 and the substrate 93, there is no suitableplace for electrodes to be disposed. In order to expose a part of thep-type semiconductor layer 92, the entire semiconductor structure willbe platformed (e.g. mesa process), such as etching a part of the n-typesemiconductor layer 90 and the active layer 91 from the above until thep-type semiconductor layer 92 is exposed. Please refer to FIG. 1B. FIG.1B is a schematic diagram illustrating the structure of a conventionallight emitting diode after being platformed. As shown in FIG. 1B, afterthe mesa process, the n-type semiconductor layer 90, the active layer91, and the p-type semiconductor layer 92 will be formed into a steppedstructure or a L-shaped structure. Next, an electrode 94 can be disposedon the n-type semiconductor layer 90, and an electrode 95 can bedisposed on the p-type semiconductor layer 92.

In the convention mesa process as described above, however, parasiticleakage current is likely to be generated on the sidewall 96 of then-type semiconductor layer 90, the active layer 91, and the p-typesemiconductor layer 92 after being etched in the mesa process, leadingto the luminous efficiency of the LED be reduced. Generally speaking,the leakage current caused by the mesa process on the sidewall 96 iscalled the mesa sidewall effect. The mesa sidewall effect may have evengreater impact on the luminous efficiency for applying to the microLEDs. Therefore, it is urgent that a new LED structure reducing theimpact of the mesa sidewall effect be provided to this industry.

SUMMARY OF THE INVENTION

The present invention provides a micro LED structure, which does notrequire the mesa process and thereby avoids the impact of the mesasidewall effect.

The present invention discloses a micro LED structure including a firstsemiconductor layer, a first electrode, a second electrode, and anactive layer. The first semiconductor layer has two opposite sidesdefined as a first surface and a second surface. The first semiconductorlayer has a doped region which is located therein and exposed on thefirst surface. A pn junction is formed between the doped region and thefirst semiconductor layer. The first electrode is located on the firstsurface and capable of electrically connecting to the firstsemiconductor layer. The second electrode is located on the firstsurface and capable of electrically connecting to the doped region. Theactive layer is adjacent to the second surface. The first semiconductorlayer is a first doping type, and the doped region is a second dopingtype. The first doping type is different from the second doping type,and the first semiconductor layer and the pn junction are located at thesame side of the active layer.

In some embodiments, the micro LED structure may further includes afirst ohmic contact layer, disposed between the first electrode and thefirst surface, which contacts the first electrode and the firstsemiconductor layer respectively. Besides, the first ohmic contact layerand the second electrode are separated on the first surface by a firstdistance, and the first distance is between 0.5 μm and 80 μm. Inaddition, in the normal direction of the first surface, the ratio of anorthogonal projection area of the first electrode to the first ohmiccontact layer may be between 0.01 and 1.5. Moreover, the first electrodeis with a first thickness, the first ohmic contact layer is with asecond thickness, the second electrode is with a third thickness, andthe third thickness may be the sum of the first thickness and the secondthickness.

In some embodiments, the second electrode may covers the doped region onthe first surface. Besides, in the normal direction of the firstsurface, the ratio of an orthogonal projection area of the secondelectrode to the doped region may be between 0.5 to 2. In addition, themicro LED structure may further includes a second semiconductor layer,and the active layer is located between the first semiconductor layerand the second semiconductor layer. The second semiconductor layer maybe the first doping type.

To summarize, the micro LED structure of the present invention forms thedoped region in the first semiconductor layer, and make the doped regionexposed on the first surface of the first semiconductor layer. In thisway, the electrodes with different electric polarities can be directlydisposed on the first surface, and can be electrically connected to thefirst semiconductor layer and the doped region, respectively. In otherwords, the micro LED structure does not require the mesa process,thereby avoiding the impact of the mesa sidewall effect and improvingthe luminous efficiency.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

FIG. 1A is a schematic diagram of a traditional LED structure.

FIG. 1B is a schematic diagram of a traditional LED structure after themesa process.

FIG. 2 is a schematic diagram of a micro LED structure in accordancewith an embodiment of the present invention.

FIG. 3 is a schematic diagram of a micro LED structure in accordancewith another embodiment of the present invention.

FIG. 4 is a schematic diagram of a micro LED structure in accordancewith further another embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating the current of a micro LEDstructure in accordance with an embodiment of the present invention.

FIG. 6 is a schematic diagram of a micro LED structure in accordancewith still another embodiment of the present invention.

FIG. 7 is a schematic diagram of a micro LED structure in accordancewith still another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The features, objections, and functions of the present invention arefurther disclosed below. However, it is only a few of the possibleembodiments of the present invention, and the scope of the presentinvention is not limited thereto; that is, the equivalent changes andmodifications done in accordance with the claims of the presentinvention will remain the subject of the present invention. Withoutdeparting from the spirit and scope of the invention, it should beconsidered as further enablement of the invention.

Please refer to FIG. 2, FIG. 2 is a schematic diagram of a micro LEDstructure in accordance with an embodiment of the present invention. Asshown in FIG. 2, the micro LED structure 1 of this embodiment may bedisposed on a substrate 20, and the micro LED structure 1 may include afirst semiconductor layer 10, a first electrode 12, a second electrode14, and the active layer 16. The substrate 20 may be a growth substrateor a temporary substrate which is transparent, but the invention is notlimited thereto. In addition, the first semiconductor layer 10 may haven-type or/and p-type doping. For the convenience of description, anexemplary example that the first semiconductor layer 10 with the n-typedoping is explained in the following embodiment.

The first semiconductor layer 10 may be a multilayer structure defined afirst surface 10 a and a second surface 10 b thereon. Taking FIG. 2 asan example, the first surface 10 a is a surface of the firstsemiconductor layer 10 facing upward, and the second surface 10 b is asurface of the first semiconductor layer 10 facing downward. Inaddition, the first semiconductor layer 10 has a doped region 100. Asthe first semiconductor layer 10 is with the n-type doping (first dopingtype), the doped region 100 should be with a p-type doping (seconddoping type), so that a pn junction 102 can be formed between the dopedregion 100 with p-type doping and the first semiconductor layer 10 withthe n-type doping. In practice, since the doped region 100 is located inthe first semiconductor layer 10, and the doping types of the dopedregion 100 and the first semiconductor layer 10 are different, the pnjunction 102 may be defined as each boundary/edge of the doped region100. For the convenience of description, FIG. 2 shows the pn junction102 located on the left boundary of the doped region 100, but thelocation of the pn junction 102 should not be a limitation to thisembodiment. For example, the bottom or the right boundaries of the dopedregion 100 can also be regarded as one instantiation of the pn junctions102.

In one example, the doped region 100 is formed by an ion implantationprocess or an ion diffusion process. For example, p-type dopants can beimplanted or diffused downward from the first surface 10 a into thefirst semiconductor layer 10 for creating the doped region 100. Thedoping concentration in the doped region 100 may be greater than 10¹⁷,and preferably be greater than 2×10¹⁸. It can be seen from FIG. 2 that apart of the first surface 10 a can be defined as the doped region 100,that is, the doped region 100 can be exposed on the first surface 10 a.In addition, the ratio in thickness of the doped region 100 to the firstsemiconductor layer 10 does not limit the invention, for example, thethickness of the first semiconductor layer 10 may be altered between2000 Å and 1 μm. In practice, since the doped region 100 is formedvertically from the first surface 10 a into the first semiconductorlayer 10, the structure of the first semiconductor layer 10 will not bedamaged by etching. Therefore, the doped region 100 and the firstsemiconductor layer 10 may be substantially coplanar on the firstsurface 10 a. In other words, the first surface 10 a will be flat at theboundary of the doped region 100.

In the above example, the doped region 100 and the first semiconductorlayer 10 can be made of the same material. In one example, the dopedregion 100 and the first semiconductor layer 10 may also be made ofdifferent materials. Besides, it is also possible to etch a groove inthe first semiconductor layer 10 in the first place, and fill the groovewith different materials to form the doped region 100. In other words,the doped region 100 and the first semiconductor layer 10 of the presentinvention should have different doping types.

Please continue to refer to FIG. 2, the first electrode 12 and thesecond electrode 14 may be on the same side of the first semiconductorlayer 10, for example, both of the first electrode 12 and the secondelectrode 14 can be disposed on the first surface 10 a. The firstelectrode 12 is capable of electrically connecting the firstsemiconductor layer 10, and the second electrode 14 is capable ofelectrically connecting the doped region 100. For the person havingordinary skilled in the art should understand the function of the firstelectrode 12 and the second electrode 12, and it will not be describedin detail in this embodiment. In an example, in order that the firstelectrode 12 is with good conductivity, there may be a first ohmiccontact layer 120 between the first electrode 12 and the first surface10 a. The first ohmic contact layer 120, for example, may contact thefirst electrode 12 and the first surface 10 a of the first semiconductorlayer 10. In practice, the doping concentration of the first ohmiccontact layer 120 can be greater than 10¹⁷, and preferably be greaterthan 2×10¹⁸.

Structurally, the first electrode 12 of this embodiment is with a firstthickness h1, the first ohmic contact layer 120 is with a secondthickness h2, and the second electrode 14 is with a third thickness h3.The second thickness h2 of the first ohmic contact layer 120 may bebetween 20 Å and 1000 Å, and the third thickness h3 may be the sum ofthe first thickness h1 and the second thickness h2. In other words, thetop surface of the first electrode 12 and the top surface of the secondelectrode 14 are approximately at the same height and can be coplanar,so the yield can be enhanced while transferring to another circuitsubstrate (not shown in figures). In addition, the total thickness ofthe micro LED structure 1 may be less than 5 and the total width of themicro LED structure 1 may be less than 100 μm. In detail, assuming thatboth the first ohmic contact layer 120 and the second electrode 14contact the first surface 10 a directly, the minimum distance betweenthe first ohmic contact layer 120 and the second electrode 14 on thefirst surface 10 a can be defined as a first distance d. The firstdistance d may preferably be between 0.5 μm and 80 μm, avoiding that thetunneling effect between the first ohmic contact layer 120 and thesecond electrode 14 is insignificant when the first distance d is lessthan 0.5 μm.

In addition, although FIG. 2 illustrates that the width of the firstelectrode 12 is the same as the width of the first ohmic contact layer120, and the width of the second electrode 14 is the same as the widthof the doped region 100, the present invention is not limited asdescribed herein. In an embodiment, the ratio of an orthogonalprojection area of the first electrode 12 to the first ohmic contactlayer 120 may be between 0.01 and 1.5 while viewing from above the firstsurface 10 a (along the normal direction of the first surface 10 a). Dueto the small size of the micro LED structure 1, the first electrode 12and the second electrode 14 may be too close causing a short circuitwhen said ratio is greater than 1.5. Besides, it can be considered thatthe first electrode 12 covers the first ohmic contact layer 120 when theorthogonal projection area of the first electrode 12 is greater than theorthogonal projection area of the first ohmic contact layer 120, and apart of the first electrode 12 may directly contact the first ohmiccontact layer 120. In the case that the total width of the micro LEDstructure 1 is less than 50 μm, the first electrode 12 may further beconnected to an external circuit (not shown). Therefore, with the largerbonding area, the bonding yield is expected to be increased, and thecurrent is concentrated in the area of the first ohmic contact layer120.

On the other hand, the above-mentioned orthogonal projection area of thefirst electrode 12 may also be smaller than the orthogonal projectionarea of the first ohmic contact layer 120. Please refer to FIG. 2 andFIG. 3 together, FIG. 3 is a schematic diagram of a micro LED structurein accordance with another embodiment of the present invention. Thedifference between the micro LED structure 1′ in FIG. 3 and the microLED structure 1 in FIG. 2 is that the size of the first electrode 12′ isdifferent from the size of the first electrode 12. As shown in FIG. 3,when the projected area of the first electrode 12′ is smaller than theprojected area of the first ohmic contact layer 120, it can be regardedthat the first electrode 12′ is located within the periphery of thefirst ohmic contact layer 120, so that the first electrode 12′ will notdirectly contact the first surface 10 a. Taking FIG. 2 as an example,when the orthogonal projection area of the first electrode 12 is exactlyequal to the orthogonal projection area of the first ohmic contact layer120, it can be regarded that the first electrode 12 just overlaps thefirst ohmic contact layer 120. Under the circumstances, the minimumdistance between the first electrode 12 and the second electrode 14 onthe first surface 10 a is the first distance d, and the first distance dcan be between 0.5 μm and 80 μm. The tunneling effect between the firstelectrode 12 and the second electrode 14 may be insignificant if thefirst distance d is less than 0.5 μm as mentioned.

Similarly, the ratio of the orthogonal projection area of the secondelectrode 14 to the doped region 100 is between 0.5 and 2 while viewingfrom above the first surface 10 a. In the case that the ratio is largerthan 2, the distance between the first electrode 12 and the secondelectrode 14 may be too close causing a short circuit because the microLED structure 1 is quite small. Please refer to FIG. 2 and FIG. 4together, FIG. 4 is a schematic diagram of a micro LED structure inaccordance with further another embodiment of the present invention. Thedifference between the micro LED structure 1″ in FIG. 4 and the microlight emitting diode structure 1 in FIG. 2 is that the size of thesecond electrode 14′ is different from the size of the second electrode14. As shown in FIG. 4, it can be regarded that the second electrode 14′covers the exposed doped region 100 of the first surface 10 a when theorthogonal projection area of the second electrode 14′ is larger thanthe orthogonal projection area of the doped region 100, and a part ofthe second electrode 14′ may directly contact the first semiconductorlayer 10 outside the periphery of the doped region 100. Under thecircumstances, the second electrode 14′ and the first semiconductorlayer 10 may be in non-ohmic contact, such as insulation or forming aSchottky junction. On the other hand, FIG. 2 shows that the orthogonalprojection area of the second electrode 14 may be smaller than or equalto the orthogonal projection area of the doped region 100. As such case,it can be regarded that the second electrode 14 is located within theperiphery of the doped region 100 exposed on the first surface 10 a, sothat the second electrode 14 will not directly contact the firstsemiconductor layer 10. In one example, the second electrode 14 coveringthe exposed doped region 100 on the first surface 10 a may facilitatewiring and alignment processes. In addition, the first electrode 12 andthe second electrode 14 may separated by more than 1 μm from the edge ofthe first surface 10 a, respectively. The distance between the electrode12 and the edge of the first surface 10 a may be unequal to the distancebetween the second electrode 14 and the edge of the first surface 10 a.

The active layer 16 is adjacent to the second surface 10 b of the firstsemiconductor layer 10. As shown in FIG. 2, the active layer 16 may beunder the first semiconductor layer 10. Since the pn junction 102 islocated within the first semiconductor layer 10, and the active layer 16is below the first semiconductor layer 10, it can be said that the firstsemiconductor layer 10 and the pn junction 102 are located on the sameside of the active layer 16, or said that the pn junction surface 102and the active layer 16 are located on the opposite sides of the secondsurface 10 b respectively. Please refer to FIG. 2 and FIG. 5, FIG. 5 isa schematic diagram illustrating the current of a micro LED structure inaccordance with an embodiment of the present invention. As shown in thefigures, when a voltage drop is applied between the first electrode 12and the second electrode 14, due to the characteristics of p-type andn-type semiconductors, current will occur at the pn junction 102, andthe current flow can be roughly expressed as the horizontal current pathC1. Although the current path C1 seems not to pass through the activelayer 16, the current can still pass through the active layer 16 locatedbelow due to the tunneling effect. In other words, different from thetraditional LED that in which the active layer is excited by the voltageand current in the vertical direction to emit light, the micro LEDstructure 1 of this embodiment is provided with the active layer 16under the current path C1, and the active layer 16 can be excited by thevoltage and current in the horizontal direction to emit light. Inparticular, under the circumstance that the LED is narrowed to amicron-size or a smaller size, because the thickness of the firstsemiconductor layer 10 is much thinner than that of the traditional LED,the current path C1 shown in FIG. 5 is closer to the active layer 16.Moreover, the ratio of the width of the first electrode 12 (or thesecond electrode 14) to the micro LED structure 1 is also greatlyincreased than the traditional LED, hence the current path C1 is majorlyparallel to the active layer 16 to make the tunneling effect moresignificant. Preferably, the distance between the bottom of the dopedregion 100 and the active layer 16 is within 2000 Å to have moreefficient tunneling effect.

In one example, the material of the active layer 16 can be, but notlimited thereto, selected from the group consisting ofAl_(x)Ga_(y)In_(1-x-y)As and Al_(x′)Ga_(y′)In_(1-x′-y′)As,Al_(x)Ga_(y)In_(1-x-y)P and Al_(x′)Ga_(y′)In_(1-x′-y′)P, GaP_(y)As_(1-y)and GaP_(y′)As_(1-y′), and/or Al_(x)Ga_(y)In_(1-x-y)N andAl_(x′)Ga_(y′)In_(1-x′-y′)N. In addition, the active layer 16 can alsobe, but not limited thereto, a DH (double heterojunction) structure, aSQW (single quantum well) structure, or an MQW (multiple quantum well)structure.

Please continue to refer to FIG. 2. In this embodiment, a secondsemiconductor layer 18 may further be provided under the active layer16, such that the active layer 16 is located between the firstsemiconductor layer 10 and the second semiconductor layer 18. Thisembodiment is not limit by the doping type of the second semiconductorlayer 18. For example, the doping type of the second semiconductor layer18 may be n-type or p-type, and even the second semiconductor layer 18may be undoped. Preferably, in order to improve the luminous efficiencyof the micro LED structure 1, the doping type of the secondsemiconductor layer 18 can be opposite to the doping type of the dopedregion 100, and be the same as that of the first semiconductor layer 10.The doping concentration of the second semiconductor layer 18 may beless than or equal to 10¹⁷. In an example, the material of the firstsemiconductor layer 10, the first ohmic contact layer 120, and thesecond semiconductor layer 18 may be selected fromAl_(x)Ga_(y)In_(1-x-y)As, Al_(x)Ga_(y)In_(1-x-y)P, GaP_(y)As_(1-y), orAl_(x)Ga_(y)In_(1-x-y)N. The materials of the first semiconductor layer10, the first ohmic contact layer 120, and the second semiconductorlayer 18 can be the same or different.

In addition, in the micro LED structure 1 shown in FIG. 5, it is furtherdescribed that the second semiconductor layer 18 may further include asub-layer 180 and a dielectric layer 182. The refractive index of thesub-layer 180 may be between the refractive index of air and therefractive index of the second semiconductor layer 18. The surface ofthe sub-layer 180 and the dielectric layer 182 can be flat. However, inorder to increase the light extraction efficiency, the surfaces of thedielectric layer 182 and a dielectric layer 182 can be roughened orprovided with optical structures. In practice, the refractive index ofthe material of the dielectric layer 182 is smaller than the refractiveindex of the second semiconductor layer 18, and also smaller than therefractive index of the sub-layer 180. The dielectric layer 182 may be amultilayer structure, for example, it may be stacked with variousmaterials such as silicon oxide (SiO_(x)) and titanium dioxide (TiO₂).In one embodiment, the thickness of the dielectric layer 182 is notgreater than 2 μm.

FIG. 6 is a schematic diagram of a micro LED structure in accordancewith still another embodiment of the present invention. As shown in FIG.6, the first ohmic contact layer 120 may cover most of the area of thefirst surface 10 a of the first semiconductor layer 10, and expose thefirst surface 10 a corresponding to the position of the doped region100. The first ohmic contact layer 120 can be implemented before thesecond electrode 14 is formed, and thereafter removing a part of thefirst ohmic contact layer 120 corresponding to the position of thesecond electrode 14 by a lithography process, thereby separating thefirst ohmic contact layer 120 from the second electrode 14.

For some micro LEDs, under the condition that the wavelength of theemitted light is not absorbed by the first ohmic contact layer 120 (suchas blue light and green light), a larger first ohmic contact layer 120can be applied to increase the contact surface with the firstsemiconductor layer 10, thereby improving the electrical performance ofthe micro LED structure 1. In an embodiment, the ratio of the orthogonalprojection area of the first electrode 12 to the first ohmic contactlayer 120 may be between 0.01 and 1.5 while viewing from above the firstsurface 10 a (along the normal direction of the first surface 10 a). Forsome micro LEDs, under the condition that the wavelength of the emittedlight is absorbable by the first ohmic contact layer 120 (such as redlight), a smaller area of the first ohmic contact layer 120 can reducethe absorption of red light to enhance the luminous efficiency of thered light micro LED structure. In an embodiment, the ratio of theorthogonal projection area of the first electrode 12 to the first ohmiccontact layer 120 may be between 0.1 and 1.5 while viewing from abovethe first surface 10 a (along the normal direction of the first surface10 a).

FIG. 7 is a schematic diagram of a micro LED structure in accordancewith still another embodiment of the present invention. In addition tothe increase in the covered area of the first ohmic contact layer 120,the difference between FIG. 7 from FIG. 6 is that a part of the firstsemiconductor layer 10 is etched from the first surface 10 a at thecorresponding position of the doped region 100. As described in FIG. 6,at the position corresponding to the second electrode 14, the firstohmic contact layer 120 will be removed to expose the first surface 10a. In FIG. 7, the first semiconductor layer 10 can be further etchedfrom the first surface 10 a. Since the portion of the firstsemiconductor layer 10 adjacent to the first surface 10 a is heavilydoped, the dopant of second doping type, after said heavily dopedportion is removed, can be easily doped into the doped region 100.

It can be seen from the description of FIG. 6 and FIG. 7 that the firstohmic contact layer 120 and the first semiconductor layer 10 can besimultaneously etched in the same pattern by using the lithographyprocess, which not only increases the contact area between the firstohmic contact layer 120 and the first semiconductor layer 10, but alsoincrease the doping concentration of the doped region 100, so that theelectrical performance of the second electrode 14 can be improved.

To summarize, the micro LED structure of the present invention can formthe doped region in the first semiconductor layer, and make the dopedregion exposed on the first surface of the first semiconductor layer. Inthis way, the electrodes of different electric polarities can bedirectly disposed on the first surface, and can be electricallyconnected to the first semiconductor layer and the doped region,respectively. In other words, the micro LED structure does not requirethe mesa process, thereby avoiding the impact of the mesa sidewalleffect and improving the luminous efficiency.

What is claimed is:
 1. A micro LED structure, comprising: a firstsemiconductor layer having two opposite sides defined as a first surfaceand a second surface, and the first semiconductor layer having a dopedregion located therein and exposed on the first surface, and a pnjunction is formed between the doped region and the first semiconductorlayer; a first electrode, located on the first surface, for electricallyconnecting to the first semiconductor layer; a second electrode, locatedon the first surface, for electrically connecting to the doped region;and an active layer adjacent to the second surface; wherein the firstsemiconductor layer is a first doping type, and the doped region is asecond doping type different from the first doping type, and the firstsemiconductor layer and the pn junction are located at the same side ofthe active layer.
 2. The micro LED structure according to claim 1,further comprising: a first ohmic contact layer, disposed between thefirst electrode and the first surface, contacting the first electrodeand the first semiconductor layer respectively.
 3. The micro LEDstructure according to claim 2, wherein the first ohmic contact layerand the second electrode are separated on the first surface by a firstdistance, and the first distance is between 0.5 μm and 80 μm.
 4. Themicro LED structure according to claim 2, wherein in the normaldirection of the first surface, the ratio of an orthogonal projectionarea of the first electrode to the first ohmic contact layer is between0.01 and 1.5.
 5. The micro LED structure according to claim 2, whereinthe first electrode is with a first thickness, the first ohmic contactlayer is with a second thickness, the second electrode is with a thirdthickness, and the third thickness is the sum of the first thickness andthe second thickness.
 6. The micro LED structure according to claim 1,wherein the second electrode covers the doped region on the firstsurface.
 7. The micro LED structure according to claim 1, wherein in thenormal direction of the first surface, the ratio of an orthogonalprojection area of the second electrode to the doped region is between0.5 to
 2. 8. The micro LED structure according to claim 1, furthercomprising a second semiconductor layer, wherein the active layer islocated between the first semiconductor layer and the secondsemiconductor layer.
 9. The micro LED structure according to claim 8,wherein the second semiconductor layer is the first doping type.